Hi @maheshtare, can you check the searchable name for the attribute which should be as same as oneTimePassword? Sometimes searchable and actual attribute names will differ as below.
If somehow that is not working for you, you can use workflow to send email as well. Use “Source Account Created” trigger and trigger the workflow when active directory accouont is created for a user. Get the identity in workflow and create an email template accordingly to your need. That should work.